The present invention relates in general to lateral transistors and, more particularly, to a lateral transistor operating in bipolar mode with independent base and gate biasing.
The two most common methods of forming a transistor is to lay out the device in a vertical configuration or a lateral configuration. A vertical transistor has the advantage of superior forward current gain, .beta., and a wider frequency response when compared to the performance characteristics of a laterally formed transistor. A principle disadvantage of the vertically formed transistor is the complexity of the manufacturing process in that the regions comprising the collector and emitter must be formed at different times using carefully controlled thermal processes. The spatial separation between the emitter and collector in the bipolar transistor is also critical. In vertical transistors, this dimension is defined by thermal cycles. In laterally formed transistors, it is determined by photolithography.
A laterally formed transistor has the advantage of simplified manufacturing by forming the collector and emitter regions at the same time. Unfortunately, the lateral bipolar transistor suffers from poor forward current gain, on the order of 5 to 10, and a limited frequency response. Moreover, the forward current gain in the lateral transistor tends to decrease at relatively low values of collector current.
Hence, a need exists for an improved lateral transistor having high forward current gain over a broad range of frequencies and collector currents.